P5.090 Evaluation of a Double Rapid Test For Syphilis and HIV: SD Bioline HIV/Syphilis Duo

Abstract

Results We confirm the initially reported specificity and further narrow down its confidence interval (specificity 99.5%, 95% CI 99.4-99.6%), and show that this high specificity is valid across diverse patient categories. Here we demonstrate that differences in positive predictive values between patient categories reflect the prevalence of syphilis in these categories, and are not due to differences in specificity. In addition, in a sensitivity analysis we show that these conclusions are robust for several assumptions. Conclusion Our analysis shows that the high specificity found in the initial study, stands up after implementation in a population with a low syphilis prevalence (0.9%). Using a selected serum sample collection is therefore a valid manner in the evaluation of syphilis serological diagnostic assays. Confirmatory syphilis testing remains mandatory in low prevalence populations, even when the screening test has a very high specificity. Background Although syphilis and HIV are primarily transmitted through sexual intercourse, they can also be transmitted from mother to child during pregnancy or at delivery. Testing pregnant women for syphilis and HIV is an important public health measure to prevent vertical transmission. Several countries have included screening of pregnant women using rapid HIV testing, and recently also rapid syphilis testing. Screening pregnant women for both diseases with one test is not only desirable but could also be very convenient. We present the results of the laboratory-based evaluation of a new test: the SD Bioline HIV/Syphilis Duo. Methods We used archived serum specimens characterised as positive or negative for HIV and/or Syphilis. The gold standard positive for HIV was EIA (Vironostika ® HIV Uni-Form II Ag/Ab, bioMéri-eux) with confirmation using Western blot. The reference standard positive for syphilis was the Rapid Plasma Reagin test (RPR, bioMérieux) with confirmation using the Treponema pallidum Particle Agglutination (TPPA) assay (Fujireibio, Japan). Reference standard negatives were EIA negative and RPR negative for HIV and syphilis respectively. For Syphilis we used a total of 665 samples, including 198 positives, and for HIV we used 662 samples including 91 positives. There were 42 samples positive for both HIV and syphilis. The samples were tested with the SD Bioline HIV/Syphilis Duo by a laboratory technician blinded to the gold standard results. Results For Syphilis we observed a sensitivity of 100% (198/198) and a specificity of 99.57% (465/467). The two RPR negative/Bioline positive samples were negative for TPPA. For HIV, both the sensitivity and specificity were 100% (91/91 and 571/571 respectively). Conclusions The SD Bioline HIV/Syphilis Duo test has a good performance in archived sera. Its high sensitivity suggests that this dual test would be of use in screening programmes for syphilis and HIV. Evaluation of a DoublE

Evaluation of the SD BIOLINE HIV/syphilis Duo assay at a rural health center in Southwestern Uganda

“…A notable difference between that study and ours was that the assay was performed in centralized laboratories. Two other recent reports from California, USA and England using archived specimens noted sensitivities and specificities above 99.5% for both assays [ 14 , 15 ]. Our study contributes a validation of the assay at a peripheral health center in a resource-limited setting and adds to the growing evidence in support of the high accuracy of the assay across various settings.…”